Can I Extend a class with only private constructors?

No, you can’t extend a class that has only private constructors. Let’s see it with an example.

Shape.java

public class Shape {
 private Shape() {
  System.out.println("Inside Shape");
 }
}

Circle.java

public class Circle extends Shape {

}

Try to compile 'Circle.java', Java compiler throws following errors.

C:\Users\Documents>javac Circle.java
Circle.java:1: error: Shape() has private access in Shape
public class Circle extends Shape {
       ^
1 error

This is one of the good interview questions, usually interviewers checks your understanding on OOPS concepts. Same question can be asked like 'How can you make a class as non-extendable without using final keyword'.

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